Ubiquitin-specific protease 22 (USP22) is closely related with poor prognosis of cancer patients. However, the role of USP22 expression in nasopharyngeal carcinoma (NPC) has not been determined. The main aim of this study was to determine the role of USP22 in the pathologic processes of NPC. Immunohistochemistry (IHC), western blot (WB), and real-time polymerase chain reaction (RT-PCR) were used to measure the expression of USP22 in cell lines and tissues of NPC in comparison with expression in non-cancerous cells and tissues. USP22-specific short hairpin RNA (shRNA) was used to knock down USP22 expression in the NPC cell line CNE-1 and CNE-2. Furthermore, the impact of USP22 in cellular proliferation, growth, and cell cycle were detected respectively. WB was used to determine the role of USP22 in the AKT/GSK-3/Cyclin signaling pathway. The expression levels of USP22 were remarkably higher in NPC cell lines and tissues. With cell counting and the MTS assay, cellular growth and proliferation progression of USP22 knockdown cell line was shown to be effectively restrained. The USP22 silencing both in CNE-1 and CNE-2 cells caused them to accumulate in the G0/G1 phase of the cell cycle. USP22 knockdown was also found to modulate the AKT/GSK-3/Cyclin pathway, resulting in downregulation of p-AKT, p-GSK-3β, and cyclinD1. This study suggests that USP22 plays a critical regulatory role in the pathologic processes of NPC, and that it may be a potential biological treatment target in the future.
Keywords: AKT/GSK-3/Cyclin pathway; DUBs, Deubiquitinating Enzymes; EB, Epstein-Barr; IHC, Immunohistochemistry; NC, Negative Control; NPC, Nasopharyngeal carcinoma; Nasopharyngeal carcinoma; ORF, Open Reading Frame; RT-PCR, real-time polymerase chain reaction; USP22; USP22, Ubiquitin-specific Protease 22; WB, Western Blot; cell cycle; cell growth; cell proliferation; hSAGA, human Spt-Ada-Gcn5 acetyltransferase; shRNA, short hairpin RNA; shUSP22, small hairpin RNA of USP22.